1. Field of the Invention
The present invention relates to a fluorescent cover, in particular a light permeable fluorescent cover attached on a light emitting diode for irradiating out of the cover lights of different wavelengths from wavelength of light emitted from the diode.
2. Description of the Prior Art
For example, U.S. patent application Ser. No. 09/597,038 discloses a plastic encapsulated semiconductor light emitting device which comprises a plurality of leads, one of which is formed with a dished portion; a semiconductor light emitting element attached on a bottom surface of the dished portion for electrical connection of the light emitting element across the leads; a plastic encapsulant for sealing each end of the leads and semiconductor light emitting element; a light-permeating cover attached to an outer surface of the plastic encapsulant; and fluorescent particles contained in the cover. In this device, the semiconductor light emitting element produces a blue light that is emanated through the plastic encapsulant and reaches the fluorescent particles in the cover to activate or excite the fluorescent particles for wavelength-conversion of light emitted from the semiconductor light emitting element. As a result, the fluorescent particles generate from the cover a white light with its wavelength different from that of light from the semiconductor light emitting element. However, this light emitting device is defective in that it cannot produce a light of the satisfactory coloring balance with less amount of red component in the light.
An object of the present invention is to provide a light permeable fluorescent cover attached on a light emitting diode suitable for a display that requires sharp emission spectra or excellent colorific balance such as a transmission color liquid crystal display or a backlighting device. Another object of the present invention is to provide a light permeable fluorescent cover attached on a light emitting diode suitable for a display that requires excellent colorific balance such as a supplementary light source for a reflection color liquid crystal display. A still another object of the present invention is to provide a light permeable fluorescent cover attached on a light emitting diode for producing an eye-friendly light conformable to human physiology. A further object of the present invention is to provide a light permeable fluorescent cover attached on a light emitting diode for producing a light with the colorific tone for covering a wider chromatic area. A still further object of the present invention is to provide a light permeable fluorescent cover made at reduced cost with good quality for a light emitting diode.